Electrically identifiable electrode lead and method of electrically identifying an electrode lead

ABSTRACT

An electrically identifiable medical electrode lead. The lead includes a flexible lead body having a distal end and a connector end. The lead also includes a plurality of electrodes disposed near the distal end of the flexible lead body. The lead further includes a connector disposed at the connector end of the flexible lead body, the connector including a plurality of contacts. The lead additionally includes a plurality of conductors supported by and passing through the flexible lead body, the plurality of conductors including electrical conductors that provide paths for electrical current from the connector to the plurality of electrodes. Finally, the lead includes a memory circuit supported by the flexible lead body and being in electrical communication with a contact of the plurality of contacts in the connector.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/174,113, filed Jun. 30, 2011, now U.S. Pat. No. 8,798,768, which isincorporated herein by reference in its entirety.

BACKGROUND

The invention relates to electrically identifiable electrode leads andmethods of electrically identifying medical electrode leads, such as animplantable medical electrode lead. An exemplary implantable medicalelectrode lead can be used with an implantable pulse generator (IPG) ofan electrical stimulation system.

When a physician implants multiple leads and connects them to an IPG,for example, the positions of the leads and the characteristics of theindividual leads may be unknown, for example to the clinicianprogrammer. Thus, confusion may arise of what locations andcharacteristics of the individual leads relate to what stimulationchannel, after they have been implanted.

Currently, when information about implanted leads is recorded, it istypically done manually and before the implantation has occurred. Forexample, during surgery, a lead packaging will be opened and the brand,model, and serial number recorded by hand into the patient's medicalrecord or into a clinician programmer device. Further, a manualassignment is required of the lead connected to the bore of the IPGheader. These manual entries leave room for error in the process ofrecording information and may lead to false stimulation programming.Thus, what is needed are means and methods for accurately, quickly, andreliably determining what types of leads are connected to an IPG andtheir respective positions within the patient.

SUMMARY

In one aspect, the invention provides an electrically identifiablemedical electrode lead. The lead includes a flexible lead body having adistal end and a connector end. The lead also includes a plurality ofelectrodes disposed near the distal end of the flexible lead body. Thelead further includes a connector disposed at the connector end of theflexible lead body, the connector including a plurality of contacts. Thelead additionally includes a plurality of conductors supported by andpassing through the flexible lead body, the plurality of conductorsincluding electrical conductors that provide paths for electricalcurrent from the connector to the plurality of electrodes. Finally, thelead includes a memory circuit supported by the flexible lead body andbeing in electrical communication with a contact of the plurality ofcontacts in the connector.

In another aspect, the invention provides an electrical stimulationsystem. The electrical stimulation system includes an electricallyidentifiable medical electrode lead and an implantable pulse generatorhaving a connection for at least one lead. The electrically identifiablemedical electrode lead includes a flexible lead body having a distal endand a connector end; a plurality of electrodes disposed near the distalend of the flexible lead body; a connector disposed at the connector endof the flexible lead body, the connector including a plurality ofcontacts; a plurality of conductors supported by and passing through theflexible lead body, the plurality of conductors including electricalconductors that provide paths for electrical current from the connectorto the plurality of electrodes; and a first memory circuit supported bythe flexible lead body and being in electrical communication with acontact of the plurality of contacts in the connector.

In yet another aspect, the invention provides a method of electricallyidentifying an implantable medical electrode lead. The lead includes aflexible lead body having a distal end and a connector end. The leadalso includes a plurality of electrodes disposed near the distal end ofthe flexible lead body. The lead further includes a connector disposedat the connector end of the flexible lead body, the connector includinga plurality of contacts. The lead additionally includes a plurality ofconductors supported by and passing through the flexible lead body, theplurality of conductors including electrical conductors that providepaths for electrical current from the connector to the plurality ofelectrodes. Finally, the lead includes a memory circuit supported by theflexible lead body and being in electrical communication with at leasttwo contacts of the plurality of contacts in the connector. The methodincludes steps of coupling the lead to an electrical stimulation system;powering the at least two contacts that are in electrical communicationwith the memory circuit including electrically stimulating the at leasttwo contacts to generate a voltage difference between the at least twocontacts; and reading the identification code from the memory circuit inresponse to powering the at least two contacts.

In still another aspect, the invention provides an electricallyidentifiable medical lead extension. The electrically identifiablemedical lead extension includes a flexible extension body having aproximal end and a distal end; a proximal connector disposed at theproximal end of the flexible extension body, the proximal connectorincluding a plurality of contacts; a distal connector disposed at thedistal end of the flexible extension body, the distal connectorincluding a second plurality of contacts; a plurality of conductorssupported by and passing through the flexible extension body, theplurality of conductors including electrical conductors that providepaths for electrical current from the proximal connector to the distalconnector; and a memory circuit supported by the flexible extension bodyand being in electrical communication with a contact of the plurality ofcontacts.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial perspective view of a patient receiving treatmentwith a spinal cord stimulation system.

FIG. 2A is a perspective view of an in-line lead for use in the spinalcord stimulation system of FIG. 1.

FIG. 2B is a perspective view of a paddle lead for use in the spinalcord stimulation system of FIG. 1.

FIG. 3 is a perspective view of a lead extension for use in the spinalcord stimulation system of FIG. 1.

FIG. 4A is a block diagram of an implantable pulse generator for use inthe spinal cord stimulation system of FIG. 1.

FIG. 4B is a block diagram of an alternative implantable pulse generatorfor use in the spinal cord stimulation system of FIG. 1.

FIG. 5 is a block diagram of a clinician programmer for use in thespinal cord stimulation system of FIG. 1.

FIG. 6 is a cross section view of an in-line lead.

FIG. 7 is a side view of a proximal connector.

FIG. 8 is a longitudinal section view of a proximal connector.

FIG. 9 is a schematic diagram of three leads, each having anidentification module incorporated therein.

FIG. 10 is a diagram of an identification module embedded within anin-line lead.

FIG. 11 is a flow diagram of a method of making an identificationmodule.

FIG. 12 is an electrical schematic of an implantable pulse generatorcoupled to a lead with an identification module electrically connectedbetween two conductors of the lead.

FIG. 13 is a circuit diagram of an identification module that uses twoconductors without interrupting either of the conductors.

FIG. 14 is a circuit diagram of an identification module that uses twoconductors but includes a switch that can interrupt one of theconductors.

FIG. 15 is a flow diagram of a method of implanting an implantable pulsegenerator with one or more electrically identifiable lead.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

The invention herein relates to a medical electrode lead for anelectrical stimulation system. The electrical stimulation systemprovides stimulation to a target tissue of a patient, where the leadincludes a non-radio frequency electrical mechanism by which the leadcan be identified using wiring in the lead. In the construction shown, aspinal cord stimulation (SCS) system 100 provides electrical pulses to apatient, including to the neurons of the spinal cord of a patient,thereby providing treatment to the patient. However, other electricalstimulation systems can be used with the invention. The electricalstimulation system may provide electrical pulses to other portions of apatient's body, including a muscle or muscle group, peripheral nerves,the brain, etc.

In various implementations, the SCS system 100 includes a clinicianprogrammer (CP) 130, a patient programmer and charger (PPC) 135, and auser programmer (UP) 140. The IPG 115 communicates with any one of theCP 130, the PPC 135, and the UP 140. The CP 130 interacts with the IPG115 to develop a program (or protocol) for stimulating the patient,which may be facilitated through the use of a patient feedback device(PFD) 145. Once a protocol is developed, the PPC 135 or the UP 140 canactivate the protocol. The protocol may be stored at the IPG 115 or canbe communicated and stored at the PPC 135 or the UP 140. The PPC 135also is used for charging the IPG 115. Constructions of the IPG 115, CP130, PPC 135, and PP 140 are disclosed in U.S. patent application Ser.Nos. 13/118,764 and 13/118,775, both of which are incorporated herein byreference above.

Referring back to FIG. 1, a user may provide feedback to the CP 130 withthe PFD 145 while the CP 130 develops the protocol for the IPG 115. Inthe construction shown in FIG. 1, the PFD 145 is an ergonomic handhelddevice having a sensor (also referred to as input) 165, a controller,and a communications output 175. Further description of the PFD 145 andmethods for developing a protocol are disclosed in U.S. patentapplication Ser. Nos. 13/118,764 and 13/118,775, both of which have beenincorporated by reference above.

Referring now to FIGS. 2A and 2B, the figures show two exemplary medicalelectrode leads 110A and 110B, respectively, that can be used in the SCSsystem 100. A first common type of lead is the “in-line” lead 110A shownin FIG. 2A. An in-line lead 110A includes individual electrodes 150Aalong the length of a flexible cable 155A. A second common type of leadis the “paddle” lead 110B shown in FIG. 2B. In general, the paddle lead110B is shaped with a wide platform 160B on which a variety of electrode150B configurations are situated. For example, the paddle lead 110Bshown in FIG. 2B has two columns of four rectangular shaped electrodes150B. A paddle lead typically contains electrodes on one side only,however, in various embodiments a paddle lead 110B can includeelectrodes 150B on both sides. Furthermore, although the embodimentshown in FIG. 2B shows the electrodes 150B embedded within the paddlelead 110B, in other embodiments a paddle lead 110B can includeelectrodes 150B that are mounted on the surface. A lead extension 110C,shown in FIGS. 1 and 3, optionally connects the lead 110A, 110B to theIPG 115.

For both leads shown in FIGS. 2A and 2B, a flexible cable 155A or 155Bhas respective small conductors (e.g. wires) for the electrodes 150A or150B. The conductors are embedded within the cable 155A or 155B andcarry the electrical stimulation from the IPG 115 to the electrodes 150Aor 150B.

It is envisioned that other types of medical electrode leads 110 andelectrode arrays 120 can be used with the invention. Also, the number ofelectrodes 150 and how the electrodes 150 are arranged in the electrodearray 120 can vary from the examples discussed herein.

The leads shown in FIGS. 2A and 2B are multiple channel leads. Here, a“channel” is defined as a specified electrode 150, or group ofelectrodes 150, that receives a specified pattern or sequence ofelectrical stimuli. For simplicity, this description will focus on eachelectrode 150 and the IPG's 115 metallic housing providing a respectivechannel. When more than one channel is available, each channel may beprogrammed to provide its own stimulus to its defined electrode.

There are many instances when it is advantageous to have multiplechannels for stimulation. For example, different pain locations (e.g.,upper extremities, lower extremities) of the patient may requiredifferent stimuli. Further, some patients may exhibit conditions bettersuited to “transverse” stimulation paths, where the current paths travelacross the spinal column, while other patients may exhibit conditionsbetter suited to “longitudinal” stimulation paths, where the currentpaths travel along the spinal column. Therefore, multiple electrodespositioned to provide multiple channels can cover more tissue/neuronarea, and thereby provide better stimulation protocol flexibility totreat the patient.

It is also envisioned that the number of leads 110 can vary. Forexample, one, two, or more leads 110 can be connected to the IPG 115.The electrode arrays 120 of the leads 110, respectively, can be disposedin different vertical locations on the spine 125 to achieve longitudinalstimulation, can be disposed horizontally (or “side-by-side”) on thespine 125 to achieve transverse stimulation, or some combinationthereof.

FIGS. 4A and 4B show block diagrams of two possible constructions of theIPG 115. The IPG 115 includes a printed circuit board (“PCB”) that ispopulated with a plurality of electrical and electronic components thatprovide power, operational control, and protection to the IPG 115. Withreference to FIGS. 4A and 4B, the IPG 115 includes a communicationportion 200 having a transceiver 205, a matching network 210, andantenna 212. The communication portion 200 receives power from a powerASIC (discussed below), and communicates information to/from themicrocontroller 215 and a device (e.g., the CP 130) external to the IPG115. For example, the IPG 115 can provide bi-direction radiocommunication capabilities to allow an external programming device tosend commands to the IPG 115 and to allow the IPG 115 to send statusdata and error codes back to the external programming device.

The IPG 115, as previously discussed, provides stimuli to electrodes 150of an implanted medical electrode lead 110. As shown in FIGS. 4A and 4B,N electrodes 150 (addressed by the IPG 115 through respective channels)are connected to the IPG 115. In addition, the enclosure or housing 220of the IPG 115 can act as an electrode. The stimuli are provided by astimulation portion 225 in response to commands from the microcontroller215. The stimulation portion 225 includes a stimulation applicationspecific integrated circuit (ASIC) 230 and circuitry including blockingcapacitors and an over-voltage protection circuit. As is well known, anASIC is an integrated circuit customized for a particular use, ratherthan for general purpose use. ASICs often include processors and/ormemory blocks including ROM, RAM, EEPROM, Flash, etc. The stimulationASIC 230 can include a processor, memory, and firmware for storingpreset pulses and protocols that can be selected via the microcontroller215. The providing of the pulses to the electrodes 150 is controlledthrough the use of a waveform generator and amplitude multiplier of thestimulation ASIC 230. The stimulation portion 225 of the IPG 115receives power from the power ASIC (discussed below). The stimulationASIC 230 also provides signals to the microcontroller 215. Morespecifically, the stimulation ASIC 230 can provide impedance informationfor the channels associated with the electrodes 150, and alsocommunicate calibration information with the microcontroller 215 duringcalibration of the IPG 115. Additionally, the stimulation ASIC 230 ofthe IPG 115 can provide identification information from any connectedleads 110 that include identification modules 420 (discussed below)coupled through the electrode channels. In the construction shown inFIG. 4B, the IPG 115 includes a separate lead ID interface 232 whichincludes connections to identification modules 420 that are independentof the electrode channel connections. In this latter construction, thelead ID interface 232 is independent of the stimulation ASIC 230 andcommunicates identification information directly to the microcontroller215.

The IPG 115 also includes a power supply portion 240. The power supplyportion includes a rechargeable battery 245, fuse 250, power ASIC 255,recharge coil 260, rectifier 263 and data modulation circuit 265. Therechargeable battery 245 provides a power source for the power supplyportion 240. The recharge coil 260 receives energy from the PPC 135 viaan inductive link. The inductive link uses a primary coil connected tothe PPC 135 to transfer energy inductively to the recharge coil 260,which behaves as a secondary coil in the inductive link. The energyreceived by the recharge coil 260 is converted and conditioned to apower signal by the rectifier 263. The power signal is provided to therechargeable battery 245 via the power ASIC 255. The power ASIC 255manages the power for the IPG 115. The power ASIC 255 provides one ormore voltages to the other electrical and electronic circuits of the IPG155. The data modulation circuit 265 facilitates the charging process byallowing bidirectional communications between the IPG 115 and PPC 135via the inductive link.

The IPG 115 also includes a magnetic sensor 280. The magnetic sensor 280provides a “hard” switch upon sensing a magnet for a defined period. Thesignal from the magnetic sensor 280 can provide an override for the IPG115 if a fault is occurring with the IPG 115 and the IPG 115 is notresponding to other controllers.

The IPG 115 is shown in FIG. 4 as having a microcontroller 215.Generally speaking, the microcontroller 215 is a controller forcontrolling the IPG 115. The microcontroller 215 includes a suitableprogrammable portion 285 (e.g., a microprocessor or a digital signalprocessor), a memory 290, and a bus or other communication lines.

The IPG 115 includes memory, which can be internal to the control device(such as memory 290), external to the control device (such as serialmemory 295), or a combination of both. Exemplary memory include aread-only memory (“ROM”), a random access memory (“RAM”), anelectrically erasable programmable read-only memory (“EEPROM”), a flashmemory, a hard disk, or another suitable magnetic, optical, physical, orelectronic memory device. The programmable portion 285 executes softwarethat is capable of being stored in the RAM, the ROM, or anothernon-transitory computer readable medium such as another memory or adisc.

Software included in the implementation of the IPG 115 is stored in thememory 290. The software includes, for example, firmware, one or moreapplications, program data, one or more program modules, and otherexecutable instructions. The programmable portion 285 is configured toretrieve from memory and execute, among other things, instructionsrelated to the control processes and methods described below for the IPG115. For example, to enable a read mode of the lead identificationmodule, the programmable portion 285 executes instructions forcontrolling the IPG 115 to provide a defined frequency or modulation onthe channels that are in contact with the identification module 420. Thedefined frequency or modulation can be used to trigger a reading eventof the module 420. Once the memory code string is received, the IPG 115can process and make it available to other components, such as the CP130.

The PCB also includes a plurality of additional passive and activecomponents such as resistors, capacitors, inductors, integratedcircuits, and amplifiers. These components are arranged and connected toprovide a plurality of electrical functions to the PCB including, amongother things, filtering, signal conditioning, or voltage regulation, asis commonly known.

FIG. 5 shows a block diagram of one construction of the CP 130. The CP130 includes a printed circuit board (“PCB”) that is populated with aplurality of electrical and electronic components that provide power,operational control, and protection to the CP 130. With reference toFIG. 5, the CP includes a processor 300. The processor 300 is acontroller for controlling the CP 130 and, indirectly, the IPG 115 asdiscussed further below. Of course, other processing units, such asother microprocessors, microcontrollers, digital signal processors,etc., can be used in place of the processor 300.

The CP 130 includes memory, which can be internal to the processor 300(e.g., memory 305), external to the processor 300 (e.g., memory 310), ora combination of both. Exemplary memory include a read-only memory(“ROM”), a random access memory (“RAM”), an electrically erasableprogrammable read-only memory (“EEPROM”), a flash memory, a hard disk,or another suitable magnetic, optical, physical, or electronic memorydevice. The processor 300 executes software that is capable of beingstored in the RAM, the ROM, or another non-transitory computer readablemedium such as another memory or a disc. The CP 130 also includesinput/output (“I/O”) systems that include routines for transferringinformation between components within the processor 300 and othercomponents of the CP 130 or external to the CP 130.

Software included in the implementation of the CP 130 is stored in thememory 305 of the processor 300, RAM 310, ROM 315, or external to the CP130. The software includes, for example, firmware, one or moreapplications, program data, one or more program modules, and otherexecutable instructions. The processor 300 is configured to retrievefrom memory and execute, among other things, instructions related to thecontrol processes and methods described below for the CP 130. Forexample, the processor 300 is configured to execute instructionsretrieved from the memory 140 for establishing a protocol to control theIPG 115.

One memory shown in FIG. 5 is memory 310, which can be a double datarate (DDR2) synchronous dynamic random access memory (SDRAM) for storingdata relating to and captured during the operation of the CP 130. Inaddition, a secure digital (SD) multimedia card (MMC) can be coupled tothe CP for transferring data from the CP to the memory card via slot315. Of course, other types of data storage devices can be used in placeof the data storage devices shown in FIG. 5.

The CP 130 includes multiple bi-directional radio communicationcapabilities. Specific wireless portions included with the CP 130 are aMedical Implant Communication Service (MICS) bi-direction radiocommunication portion 320, a WiFi bi-direction radio communicationportion 325, and a Bluetooth bi-direction radio communication portion330. The MICS portion 320 includes a MICS communication interface, anantenna switch, and a related antenna, all of which allows wirelesscommunication using the MICS specification. The WiFi portion 325 andBluetooth portion 330 include a WiFi communication interface, aBluetooth communication interface, an antenna switch, and a relatedantenna all of which allows wireless communication following the WiFiAlliance standard and Bluetooth Special Interest Group standard. Ofcourse, other wireless local area network (WLAN) standards and wirelesspersonal area networks (WPAN) standards can be used with the CP 130.

The CP 130 includes three hard buttons: a “home” button 335 forreturning the CP to a home screen for the device, a “quick off” button340 for quickly deactivating stimulation being delivered by the IPG 115,and a “reset” button 345 for rebooting the CP 130. The CP 130 alsoincludes an “ON/OFF” switch 350, which is part of the power generationand management block 390.

The CP 130 includes multiple communication portions for wiredcommunication. Exemplary circuitry and ports for receiving a wiredconnector include a portion and related port for supporting universalserial bus (USB) connectivity 355, including a Type-A port and a Micro-Bport; a portion and related port for supporting Joint Test Action Group(JTAG) connectivity 360, and a portion and related port for supportinguniversal asynchronous receiver/transmitter (UART) connectivity 365. Ofcourse, other wired communication standards and connectivity can be usedwith or in place of the types shown in FIG. 5.

The CP 130 includes a touch screen I/O device 375 for providing a userinterface with the clinician. The touch screen display 375 can be aliquid crystal display (LCD) having a resistive, capacitive, or similartouch-screen technology. It is envisioned that multitouch capabilitiescan be used with the touch screen display 375 depending on the type oftechnology used.

Referring again to FIGS. 2A, 2B, and 3, the figures show constructionsof implantable leads 110A (in-line lead), 110B (paddle lead), and 110C(lead extension), all of which have an identification module supportedtherein. For simplicity, the subsequent discussion will refer in generalto the various types of leads using the generic identifier 110, however,the principles discussed herein are, for the most part, applicable toany of the three types of leads 110A, 110B or extensions 110C identifiedabove as well as other types of implantable leads.

In various constructions, a lead 110A, 110B includes a flexible leadbody 112A, 112B having a distal end 114A, 114B and a connector end 116A,116B. At the connector end 116A, 116B is a connector 118A, 118B whichconnects to the IPG 115 or to lead extension 110C. In variousembodiments, the connector 118A, 118B includes one or more contacts118D, which make electrical contact with complementary mating contactsin an appropriate receptacle such as in the IPG 115 or lead extension110C. In certain embodiments, the contacts 118D are bands that encirclethe connector end 116A, 116B (FIGS. 2A and 2B). At the distal end 114A,114B are one or more electrodes 150A, 150B, each of which can beindividually stimulated. The lead extension 110C includes a flexibleextension body 112C with a distal end 114C, which couples to the lead110A, 110B, and a proximal end 116C, which couples to the IPG 115. Theproximal end 116C includes a connector 118C to connect to the IPG 115and the distal end 114C includes a connector 119 to connect to a lead110A, 110B. In various embodiments, the connector 118C includes one ormore contacts 118D as described above and as shown in FIG. 3. Theelectrodes 150B of the paddle-style lead 110B are arranged on the faceor platform 160 portion of the lead 110B. Each of the plurality ofelectrodes 150A, 150B is connected to a respective conductor 430 (e.g.wire), where the conductors 430 run through a flexible cable 155A, 155B.The flexible cable 155A, 155B couples to an implantable pulse generator(IPG) 115 via a suitable connector, although in some constructions leadextensions 110C are used to connect leads 110A, 110B indirectly to theIPG 115. In various constructions, an identification module 420 includesa memory circuit for storing an identification code. The identificationmodule 420 may be located in various places on the lead 110A, 110B,although in one construction the identification module 420 is located inor near the connector 118A, 118B in the vicinity of the contacts 118D(FIGS. 2A, 2B) and in some constructions the identification module 420may be directly coupled to the contacts (FIG. 8). In the lead extension110C, the identification module 420 may also be located in variousplaces, although in one construction the identification module 420 islocated in the connector 118C portion of the lead extension 110C (FIG.3).

In an alternative to the IPG 115, in some constructions the leads 110A,110B can receive electrical stimuli from an external pulse generator(EPG) 115A (also referred to a trial stimulator) through one or morepercutaneous lead extensions (FIG. 1). An EPG 115A may be used during atrial period or when the amount of stimulation provided to the patient105 would drain the power storage device in short durations.

In various constructions, the identification module 420 may be embeddedwithin the body of a lead 110A, 110B, or 110C. In one construction of anin-line lead 110A, the cross-section of which is shown in FIG. 6, thelead 110A includes an outer wall 440 and a cavity 445 in the centerthrough which the conductors 430 run. In one particular construction,the wall 440 is sufficiently thick so as to accommodate theidentification module 420 therein (see, e.g., FIG. 6). In general,in-line leads 110A include a plurality of electrodes that typicallyinclude circumferential bands of conductive material wrapped around orembedded in an insulating body, where the electrodes are spaced apartalong the length of the lead. In some constructions, the identificationmodule 420 is located in the space between contacts 118D (FIGS. 2A, 2B),generally embedded within insulating material of the lead 110A, 110B orextension 110C (FIG. 6).

In the constructions in which an identified in-line lead 110A has anidentified extension lead 110C attached to it, the IPG 115 (or EPG)reads separate identification modules 420 associated with both thein-line lead 110A and the extension lead 110C. To facilitate separatereading of each identification module 420, in some constructions, theidentification module 420 in the extension lead 110C is located on aseparate set of conductors 430 than the identification module 420 in theprimary lead 110A (FIG. 9).

The identification module 420 in certain constructions may beencapsulated with a protective material prior to, or coincident with,being embedded in the insulating material of the lead 110A. In variousconstructions, the identification module 420 is encapsulated in amaterial such as glass, ceramic, polymer, stainless steel, or othermaterial. Glasses suitable for hermetically sealing and encapsulatingthe identification module 420 are manufactured, for example, by Schottglass of Germany. Bio-compatible polymers may also be used toencapsulate and hermetically seal the identification module 420. Forexample, FIG. 10 schematically depicts a glass-encapsulatedidentification module 420 disposed between two contacts 118D in theconnector end of an in-line lead 110A. The encapsulated identificationmodule 420 has two leads to which conductors can be welded or attachedthrough some other means during lead assembly, or the leads of theidentification module 420 can be directly connected to contacts 118D onthe connector 118A, 118B, 118C (FIG. 8).

Known materials and methods already in use for construction offeed-through terminals for implantable medical devices can be used toencapsulate the module 420. The material may be selected to have one ormore of the following properties: (1) biocompatibility with the tissuethat the lead will be implanted into; (2) low fluid permeability,including the ability to prevent the ingress of bodily fluids into ornear the module 420 and the ability to provide a suitable mechanical andfluid seal with respect to the electrical feed-through terminals throughwhich electrical connections are established between the identificationmodule 420 and electrical conductors in the lead 110; (3) MRIcompatibility; heat stability during manufacturing (up to about 300° F.)and use; and (4) protection against leakage current and shortcircuiting. Thus, the identification module 420 can be hermeticallysealed and provide suitable electrical connections thereto.

In general the identification module 420 (with encapsulation) istypically small enough to fit within whatever portion of the lead 110 itis placed into. In one construction the identification module 420includes an EPROM. Other memory modules and various module sizes areenvisioned to be possible for the identification module 420.

Before proceeding further, it should be understood that the stepsdiscussed in connection with FIGS. 11 and 15 will be discussed in aniterative manner for descriptive purposes. Various steps describedherein with respect to the processes of FIGS. 11 and 15 are capable ofbeing executed in an order that differs from the illustrated serial anditerative manner of discussion. It is also envisioned that not all stepsare required as described below, that other steps may intervene thesteps that are listed, and that one or more of the steps described withrespect to each of the processes of FIGS. 11 and 15 can be carried outat the same time.

FIG. 11 shows a flowchart of one implementation of a method 1100 ofmaking an identification module 420. A first step 1110 is providing anidentification chip with electrical terminals and correspondingelectrical conductors. A second step 1120, if necessary, is providingthermal protection for the identification chip before encapsulation. Athird step 1130 is encapsulating and hermetically sealing theidentification chip with a suitable bio-compatible, non-porous material.A fourth step 1140 is establishing electrical connections between theidentification chip electrical conductors and medical electrode leadconductors. A fifth step 1150 is molding or otherwise forming abio-compatible lead body around the hermetically sealed identificationchip, the identification chip electrical conductors, and the medicalelectrode lead conductors.

FIG. 12 shows the electrical environment of the identification module420 and FIGS. 13-14 show possible arrangements for a two-contact (FIG.13) and a three-contact (FIG. 14) circuit for use in the identificationmodule 420.

FIG. 12 shows a simplified circuit model of an IPG 115 having a lead 110attached thereto, the lead 110 having an identification module 420electrically connected between two electrodes 150 of the lead 110. Thecircuit model also includes the capacitance between the channels, whichin this construction is typically tens of picofarads, as well as theresistance/impedance of the tissue (R_(TISSUE)), which in variousconstructions is between hundreds of ohms and several kilo-ohms.

One difficulty that arises from the electrical environment in which theidentification module 420 operates is in powering the module 420, sincethe IPG 115 generates current, in some embodiments, instead of voltage.The voltage drop between the channels driving the module can beespecially low if the tissue impedance is low. Thus, if the tissueimpedance is 100Ω and the current delivered is 50 μA, then the voltagedrop may be as low as 5 mV: 100Ω×50 μA=5 mV. Accordingly, in someinstances a “powering phase” may be required to build up an appropriatevoltage in the module before reading the memory chip.

On the other hand, the electrical environment shown in FIG. 12 alsoindicates an advantage for the identification module 420, in someenvironments. Since there is a low impedance between the module 420 andthe clamping circuit of the IPG 115, the module can rely on the voltageclamp of the IPG 115 without having to provide a voltage clamp circuitinside the identification module 420.

The construction of a two-contact circuit shown in FIG. 13 includes fivecircuit elements: a filter 470, a power converter 475, a communicationscircuit 480, a memory unit 485, and a load switch 490. The first twoelements, filter 470 and power converter 475, take the incoming currentand convert it to a voltage that is usable by the rest of the circuitry.The filter 470 has characteristics to prevent the identification module420 from turning on during normal stimulation, while enabling the powerconverter 475 when the channels are driven in a specific manner. Thecommunications circuit 480 transfers information from the memory unit485 to the IPG 115 via load modulation using the load switch 490. In oneconstruction, to read data from the memory unit 485 the IPG monitors thevoltage drop between the two channels shown in FIG. 13. Thecommunications circuit 480 opens and closes the load switch 490 in apredetermined pattern to transmit a code indicative of the leadidentification (LID) for that lead 110. The opening and closing of theload switch 490 leads to comparable changes in the voltage that isrequired to maintain the constant current output of the channels.Accordingly, the time-based pattern of changes in voltage is recordedand decoded to determine the LID. In various constructions, the IPG 115stores the information obtained from the lead(s) and/or transmits theinformation to another device such as CP 130, PPC 135, and/or UP 140 forsubsequent review or retrieval by a health care provider.

A three-contact circuit (a construction of which is shown in FIG. 14)includes the same elements as the two-contact circuit and includes twoadditional elements, a signal detect circuit 495 and a channel switch500. If an incoming read signal is detected by the signal detect circuit495, the signal detect circuit opens the channel switch to permit thecurrent-to-voltage conversion to proceed more quickly. When notactivated, the channel switch 500 would default to a “closed” state.

In general, in the constructions of the identification module 420disclosed herein there is no need for additional feed-through terminalsor lead contacts in order to allow lead identification. In other words,the identification module 420 uses the existing lead contacts for powerto and communication with the identification module 420. When theidentification module 420 is not communicating, the module 420 is“transparent” to the stimulation circuitry of the IPG 115. In variousconstructions, the identification module 420 has an impedance greaterthan 1 MΩ between its contacts when not being used.

As discussed above, constructions of the identification module 420 canbe made using two contacts or three contacts, although in general theuse of two contacts would be more desirable than three contacts from thestandpoint of easier assembly with two contacts.

In various constructions, the identification module 420 is driven usinga charge-balanced waveform, using either symmetric or asymmetricwaveforms. In addition, the identification module 420 is generallydriven with a sub-threshold current amplitude, e.g. using a current of50 μA or less per phase. Likewise, the identification module 420 shouldbe protected from currents arising in tissues from incoming externalsources such as those associated with defibrillation pulses,electrocautery, or MRI. In general, the identification module 420 iscapable of being driven by the normal output circuitry of the IPG 115,although additional circuitry may be required inside the IPG 115 forreading the identification data from the memory unit 185 of theidentification module 420.

In various constructions the identification module 420 is capable ofbeing read multiple times over the lifetime of the lead 110A, 110B.Although less preferred, one-time-read features, such asintentionally-blown fuses, can be included in the identification module420.

As discussed above, the identification module 420, in someconstructions, can be capable of communicating in the presence of atissue impedance as low as 100Ω (target) between the leads to which thecircuit is connected. In one construction, the identification module 420is capable of storing up to 32 bytes of data, equal to 256 bits,although other levels of storage are also possible.

The above discussion describes locating the identification module 420 atthe region of the lead 110A, 110B that includes the connector contacts118D. Nevertheless, in various constructions the identification module420 is located in other portions of the lead 110A, 110B such as theflexible lead body 155A, 155B or the distal end 114A, 114B, 114C.

The identifiable leads 110A, 110B, 110C disclosed herein can be used aspart of means and methods for accurately, quickly, and reliablydetermining the types of leads that are connected to an implantablepulse generator (IPG) 115 and, in conjunction with positionalinformation that is entered when each lead is implanted, theirrespective positions within the patient. Additionally, the abovedescription provides an electronic identification system for implantableneurostimulation leads that is physically integrated into the lead body.Although the disclosure uses in-line leads 110A as examples, thedisclosed methods and apparatus are equally applicable to other types ofmedical electrode leads, such as paddle-style leads 110B and extensionleads 110C.

The invention herein relates to an electrical stimulation system forproviding stimulation to target tissue of a patient. The systemdescribed in detail herein is a spinal cord stimulation (SCS) system forproviding electrical pulses to the neurons of the spinal cord of apatient. However, many aspects of the invention are not limited tospinal cord stimulation. The electrical stimulation system may providestimulation to other body portions, including a muscle or muscle group(including heart muscle, e.g. as part of a pacemaker), nerves, thebrain, and other portions of the body.

In various constructions, the identification module 420 does not usenon-contact, radio-based communication to interact with the IPG 115.Instead, the identification module 420 communicates with the IPG 115directly via electrical connections, for example by connecting to thecontacts 118D on the connector or the conductors 430 that connect theelectrodes 150A, 150B with the IPG 115. In some constructions, theidentification module 420 is connected to the conductors 430 themselvesand in other constructions to the contacts 118D or electrodes 150, whichin turn may be connected to the conductors 430.

In still other constructions, the identification module 420 is connectedto a plurality (usually two) of contacts 118D that are not connected toconductors 430 or electrodes 150. In this latter case the operation ofthe identification module 420 would be less complicated since therewould not be the difficulties associated with the low impedance betweenconductors 430 or electrodes 150 that is otherwise present. However, inthis construction there may be two additional contacts 118D on theconnector at the proximal end of the lead, which would be lessdesirable.

In use, leads and/or extensions send required data including, withoutlimitation, a model number and a serial number to the IPG 115 and thento a device such as a clinician programmer 130 without having humaninteraction, which will reduce the time it takes for recording thisinformation as well as the chance for error in recording such data.

Prior to or during the process of surgical implantation, each lead isimplanted and connected to the IPG 115 (or EPG), which device then readsself-identifying data from the identification module 420 and cantransmit this information to an external device such as CP 130. Thisprocess is then repeated for each lead that is implanted.

In various embodiments, the invention includes a method 1500 ofimplanting an identifiable lead, which method 1500 includes thefollowing steps (see also FIG. 15):

A first step 1510 of providing an electrode lead having circuitry and/orintegrated circuits incorporated therein, wherein the circuitry and/orcircuits uniquely identify the lead 110.

A second step 1520 in which, during surgical implantation, a first lead110 is connected to the IPG 115 and it is reported through the IPG 115to the clinician programmer 130 (or other external device) that thefirst lead has been connected to the IPG 115 as well as theidentification information (the lead identification, LID) obtained fromthe implanted lead 110.

A third step 1530 in which the physician or technician manually selectsor inputs a first lead 110 implant position in the patient correspondingto the connected first lead 110 and stores this body location (BL). ThisBL will be stored (e.g. on the CP 130) along with the LID code that iselectronically read from the lead 110.

A fourth step 1540 in which the clinician programmer 130 saves/storesdata corresponding to the position of the implanted first lead 110.

A fifth step 1550 in which, during surgical implantation, a second lead110′ is connected to the IPG 115 and its presence is reported throughthe IPG 115 to the clinician programmer 130.

A sixth step 1560 in which the physician or technician manually selectsor inputs a second lead 110′ implant position in the patientcorresponding to the connected second lead 110′.

A seventh step 1570 in which the clinician programmer 130 saves/storesdata corresponding to the position of the implanted second lead 110′.

An eighth step 1580 in which the clinician programmer 130 is programmedor configured to automatically recognize which lead is connected towhich port of the IPG 115 and correspondingly provide stimulation pulseshaving the correct stimulation parameters to the leads.

The leads 110 do not have to be attached to the IPG 115 in anyparticular order, since each lead 110 is capable of being uniquelyidentified using electronic means. As noted above, the BL of aparticular lead is stored along with the LID for that lead, in additionto the Connector Number (CN) on the IPG 115 to which the lead 110 isattached. This information can be stored in one or more of the IPG 115,CP 130, PPC 135, or UP 140.

In various constructions, upon reading of an LID code, the CP 130, PPC135, or UP 140 prompts a user (e.g. physician or technician) to assign aBL code to that particular lead. However, at some point (e.g. duringprogramming of the IPG 115), the LID codes are synchronized with otherstored information (e.g. CN, BL) on the IPG 115 so that such informationwill be available independent of which external device (e.g. which CP130, PPC 135, or UP 140) is used. Thus, information including LID, CN,and BL is transmitted between the various elements of the system 100,e.g. by wired or wireless communication as appropriate, either as anautomatic feature during communication or in response to a specificrequest or during a synchronization step.

During implantation, the physician or technician repeats the datareading and recording steps for each implanted lead. LID codes forextension leads, if any, are read and assigned together with theattached stimulation lead(s).

As discussed above, during implantation information regarding theposition of implanted leads 110 is entered by a physician or clinician,e.g. after being prompted by a device such as the CP 130, PPC 135, or UP140. In addition to the location (e.g. regarding which vertebra the lead110 is implanted next to) other information that can be entered includesorientation of the lead 110. The orientation might be expressed relativeto a reference point (e.g. the spinal column) including an indication ofwhether the lead 110 has its distal end 114A, 114B pointing up or down,left or right, or at a particular angle. The information regarding theposition and orientation can then be used later when programming thelead 110.

Thus, in various constructions the invention provides a useful and novelsystem and method of identifying a lead and/or extension of anelectrical stimulation system. Various features and advantages of theinvention are set forth in the following claims.

What is claimed is:
 1. A method of electrically identifying animplantable medical electrode lead, the method comprising: powering, viaan electrical stimulator, at least two contacts that are in electricalcommunication with a memory circuit of an implantable medical electrodelead coupled to the electrical stimulator, wherein the electricalstimulator and the implantable medical electrode lead are both implantedinside a body of a patient, and wherein the powering compriseselectrically stimulating the at least two contacts to generate a voltagedifference between the at least two contacts; and reading anidentification code from the memory circuit in response to powering theat least two contacts, thereby identifying a type of the implantablemedical electrode lead.
 2. The method of claim 1, wherein theimplantable medical electrode lead further comprises a power converterin an electrical circuit with the memory circuit and wherein poweringthe at least two contacts that are in electrical communication with thememory circuit further comprises powering the at least two contacts thatare in electrical communication with the memory circuit to increase avoltage in the power converter.
 3. The method of claim 1, whereinreading the identification code from the memory circuit in response topowering the at least two contacts comprises reading the identificationcode from the memory circuit using load modulation.
 4. The method ofclaim 1, further comprising obtaining at least one of a body locationand an electrode orientation for the lead.
 5. The method of claim 1,wherein the implantable medical electrode lead includes an elongateconnector that is configured to be connected to the electricalgenerator, and wherein the memory circuit is embedded within theelongate connector.
 6. The method of claim 5, wherein the implantablemedical electrode lead further includes a plurality of contacts that arelocated on the elongate connector, the plurality of contacts includingthe at least two contacts, wherein each of the contactscircumferentially surrounds the elongate connector.
 7. The method ofclaim 6, wherein the memory circuit is disposed between the at least twocontacts.
 8. An electrically identifiable medical lead extension,comprising: a flexible extension body having a proximal end and a distalend; a proximal connector disposed at the proximal end of the flexibleextension body, the proximal connector comprising a plurality ofcontacts; a distal connector disposed at the distal end of the flexibleextension body; a plurality of conductors supported by and passingthrough the flexible extension body, the plurality of conductorsincluding electrical conductors that provide paths for electricalcurrent from the proximal connector to the distal connector; and amemory circuit supported by the flexible extension body and being inelectrical communication with at least two of the contacts of theplurality of contacts, wherein the memory circuit is embedded in theflexible extension body and located in between the at least two of thecontacts.
 9. The electrically identifiable medical lead extension ofclaim 8, further comprising a filter and a power converter in anelectrical circuit with the memory circuit.
 10. The electricallyidentifiable medical lead extension of claim 9, further comprising acommunications module in an electrical circuit with the memory circuit.11. The electrically identifiable medical lead extension of claim 8,wherein the memory circuit stores an identification code.
 12. Theelectrically identifiable medical lead extension of claim 8, wherein thememory circuit is hermetically sealed within the flexible extensionbody.
 13. The electrically identifiable medical lead extension of claim8, wherein the memory circuit is sealed in glass within the flexibleextension body.
 14. A medical system, comprising: an implantable medicalelectrode lead implanted inside a body of a patient, wherein theimplantable medical electrode lead includes at least two contacts and amemory circuit that is in electrical communication with the at least twocontacts; and an electrical stimulator implanted inside the body of thepatient, the electrical stimulator being electrically coupled to theimplantable medical electrode lead to deliver electrical stimulation tothe patient, wherein the electrical stimulator is configured to: powerthe at least two contacts by electrically stimulating the at least twocontacts to generate a voltage difference between the at least twocontacts; and read an identification code from the memory circuit inresponse to the at least two contacts being powered, thereby identifyinga type of the implantable medical electrode lead.
 15. The medical systemof claim 14, wherein the implantable medical electrode lead furthercomprises a power converter in an electrical circuit with the memorycircuit, and wherein the electrical stimulator is configured to powerthe at least two contacts that are in electrical communication with thememory circuit to increase a voltage in the power converter.
 16. Themedical system of claim 14, wherein the electrical stimulator isconfigured to read the identification code from the memory circuit usingload modulation.
 17. The medical system of claim 14, wherein theelectrical stimulator is configured to obtain, via electricalcommunication with the memory circuit, at least one of: a body locationand an electrode orientation for the lead.
 18. The medical system ofclaim 14, wherein the implantable medical electrode lead includes anelongate connector that is configured to be connected to the electricalgenerator, and wherein the memory circuit is embedded within theelongate connector.
 19. The medical system of claim 14, wherein theimplantable medical electrode lead further includes a plurality ofcontacts that are located on the elongate connector, the plurality ofcontacts including the at least two contacts, wherein each of thecontacts circumferentially surrounds the elongate connector.
 20. Themedical system of claim 14, wherein the memory circuit is disposedbetween the at least two contacts.